Adsorption of multivalent ions on charged Langmuir monolayers

Cuvillier, Nicolas; Bonnier, M.; Rondelez, F.; Paranjape, D. V.; Sastry, Murali; Ganguly, P.

doi:10.1007/bf01188937

Cited by 16 publications

(28 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At low ionic concentration, the original PB equation is recovered. Simple analytical relations between the surface charge density and the counterion concentration at the surface are obtained, in agreement with recent experiments [12].Consider an asymmetric electrolyte consisting of negative multivalent ions of charge −ze, and positive monovalent ions of charge e, where e is the electron charge. The bulk concentration of the negative and positive ions is c b and zc b , respectively, as implied by charge neutrality.…”

supporting

confidence: 86%

“…The theoretical results presented here are relevant to recent experiments [12] where large multivalent ions are adsorbed onto a charged Langmuir monolayer. Large polyanions such as H 3 PW 12 O 40 (phosphotungstic acid) dissolved in an aqueous subphase are attracted to a cationic Langmuir monolayer such as a fatty amine surfactant (C 20 H 41 -NH 2 ), spread at the water/air interface.…”

mentioning

confidence: 74%

See 1 more Smart Citation

Steric Effects in Electrolytes: A Modified Poisson-Boltzmann Equation

1997

View full text Add to dashboard Cite

The adsorption of large ions from solution to a charged surface is investigated theoretically. A generalized Poisson-Boltzmann equation, which takes into account the finite size of the ions is presented. We obtain analytical expressions for the electrostatic potential and ion concentrations at the surface, leading to a modified Grahame equation. At high surface charge densities the ionic concentration saturates to its maximum value. Our results are in agreement with recent experiments.PACS numbers: 61.20. Qg,82.65.Dp,82.60.Lf The interaction between charged objects (interfaces, colloidal particles, membranes, etc) in solution is strongly affected by the presence of an electrolyte (salt) and is of great importance in biological systems and industrial applications [1,2]. The main effect is screening of the Coulomb interaction characterized by the so-called Debye-Hückel screening length [3], which depends on the ionic strength of the solution. The Deryaguin-LandauVerwey-Overbeek theory, based on the competition between screened Coulomb and attractive van der Waals interactions, has been very successful in explaining the stabilization of charged colloidal particles [4].One of the most widely used analytical method to describe electrolyte solutions is the Poisson-Boltzmann (PB) approach [5]. For low electrostatic potentials (less than 25 mV), the PB equation can be linearized and yields the Debye-Hückel theory [3]. The PB is a continuum mean-field like approach assuming point-like ions in thermodynamic equilibrium and neglecting statistical correlations. This theory has been successful in predicting ionic profiles close to planar and curved surfaces and the resulting forces. However, it is known to strongly overestimate ionic concentrations close to charged surfaces. In particular, this shortcoming of the PB theory is pronounced for highly charged surfaces and multivalent ions.Since the PB equation does not take into account the finite size of the adsorbing ions, the ionic concentration close to the surface can easily exceed the maximal allowed coverage by orders of magnitude. Several attempts have been proposed to include the steric repulsion in order to improve upon the PB approach [6,7]. One of the first attempts to incorporate steric effects is the Stern layer modification [6,8] of the PB approach. Steric effects are introduced by excluding the ions from the first molecular layer close to the surface. However, it seems difficult to improve on this method in a systematic way. More recent modifications [6,7,[9][10][11] rely either on Monte Carlo computer simulations or on numerical solutions of integral equations (the "hypernetted chain" equation [9]). These approaches involve elaborate numerical calculations and lack the simplicity of the original PB approach.In this Letter, we propose a simple way to include steric effects in the original PB approach. This modified PB equation clearly shows how ionic saturation takes place close to a charged surface. The equation is derived for 1:z asymmetric and z:z symmetric...

show abstract

supporting

confidence: 86%

mentioning

confidence: 74%

Steric Effects in Electrolytes: A Modified Poisson-Boltzmann Equation

1997

View full text Add to dashboard Cite

show abstract

“…This cannot be obtained by the Poisson -Boltzmann theory. However, in the above experiment, for a larger area per eicosylamine (small |) it was found that more counterions approach the charged plane than are necessary to compensate the charge of the eicosylamine headgroups [8,9] (data not shown in Fig. 6).…”

Section: Discussionmentioning

confidence: 70%

“…The evaluation of the different theoretical approaches can only be made by comparison of the theoretical results with experimental data. The experiments using neutron diffraction [43] and X-rays [8,9,44] show accumulation of the counterions in the vicinity of the charged plane and a rapid decrease of the density as the distance from the plane increases. Recently, experiments with large multivalent phosphotungstate ions in contact with a highly charged plane were performed [8,9].…”

Section: Discussionmentioning

confidence: 99%

Thickness of electrical double layer. Effect of ion size

Bohinc¹,

Kralj‐Iglič²,

Iglič³

2001

Electrochimica Acta

247

157

View full text Add to dashboard Cite

The thickness of a single flat electrical double layer is considered. The electrostatic mean field and the excluded volume effect are taken into account. A simple statistical mechanical approach is used, where the particles in the solution are distributed over a lattice with an adjustable lattice constant. Different sizes of ions are described by different values of the lattice constant. Two measures are introduced that describe an effective thickness of the electrical double layer: a distance where the density of the number of counterions drops to a chosen fraction of its maximal value, and a distance defining a region that contains a chosen fraction of the excess of the counterions. It is shown that the effective thickness of the electrical double layer increases with increasing counterion size and with decreasing bulk concentration of ions, whereas increasing the surface charge may cause either a decrease or an increase of the effective thickness. It is shown that the description of the effective thickness of the electrical double layer by the Debye length differs qualitatively from the description presented for low bulk concentrations of ions.

show abstract

“…Recently, experiments with a solution of large phosphotungstate ions PW 12 figure 1) is around 1 nm [2,3], so the range of values of the parameter l < 1 nm given in figure 3 seems to be a reasonable selection. In the above-mentioned experiments of Cuvillier et al the pH value of the solution of phosphotungstate ions was very low [4,23], so the amine group of eicosylamine facing the solution was fully ionized. Thus the head-group plane of the eicosylamine monolayer was highly positive.…”

Section: Theorymentioning

confidence: 92%

Orientation of multivalent ions near charged planar surfaces

Razinger¹,

Iglič²,

Kralj‐Iglič³

2006

J. Phys. A: Math. Gen.

View full text Add to dashboard Cite

A solution of large multivalent ions in contact with a planar charged surface is considered theoretically. Using a simple three-state model for the orientation of the multivalent ions in the gradient of an electric field and applying the methods of statistical physics, we show that the internal charge distribution within a single multivalent ion with the charges located at well-separated positions may lead to the orientational ordering of multivalent ions near the charged planar surface.

show abstract

Adsorption of multivalent ions on charged Langmuir monolayers

Cited by 16 publications

References 9 publications

Steric Effects in Electrolytes: A Modified Poisson-Boltzmann Equation

Steric Effects in Electrolytes: A Modified Poisson-Boltzmann Equation

Thickness of electrical double layer. Effect of ion size

Orientation of multivalent ions near charged planar surfaces

Contact Info

Product

Resources

About